| The International Thermonuclear Experimental Reactor(ITER)is the largest nuclear fusion experimental facility in the world.It aims to verify the feasibility of the controllable nuclear fusion technology in engineering.As one of the important subsystems of ITER,poloidal field power supply system plays an important role in plasma formation,ohmic heating and configuration control.The converter device which constitutes ITER poloidal field power supply covers a large area and its control system is complex.During the test of the converter,the field layer monitoring system in the control system needs to communicate with the local controller in real time(period less than 1ms),and complete the acquisition and control of thousands of analog and digital signals.The performance of the field layer equipment affects the whole poloidal field.The safe and stable operation of power supply system requires the selection of appropriate field bus equipment to complete the above work.In order to meet the above requirements,on the premise of fully understanding the topology,operation mode and control system architecture of ITER poloidal field converter,this paper firstly introduces several methods to improve the real-time and reliability of common industrial Ethernet fieldbus,analyses several mainstream Industrial Ethernet Fieldbus on the market and compares their performances,and according to ITER poloidal field converter device.The EtherCAT bus is chosen as the communication protocol of the field monitoring system for its distribution characteristics and control requirements.Secondly,according to the operation principle of the selected field bus,the influencing factors of the real-time performance of the bus network are analyzed,and the real-time performance of the bus in different classical topological networks is simulated and compared.At the same time,the correctness of the theoretical analysis is verified by setting up an experimental platform for experimental testing.The experimental results show that the realtime performance of EtherCAT bus is higher than that of other topologies when using ring topology,and the maximum control period of field layer monitoring system of converter with ring topology is about 20?s,which can meet the needs of 1ms communication cycle.Thirdly,according to the common redundancy mode of EtherCAT bus network,based on the typical topological network,three redundant network schemes with different topologies are designed and compared,and the reliability of three heterogeneous topological networks varying with the number of nodes is simulated by MATLAB software.The simulation results show that the reliability of three kinds of heterogeneous topological redundant networks decreases gradually with the expansion of network scale,but compared with the other two networks,the ring topological network still has better reliability in small EtherCAT networks.Moreover,the average pre-fault time of the converter field layer monitoring system using ring network is 7.62 years,which is much higher than the continuous operation time of the converter.Finally,based on the analysis results of real-time and reliability,the ring topology is selected as the fieldbus hardware network topology of the converter field layer monitoring system,and the topology map is drawn.In addition,an experimental platform was built to complete the communication configuration of the host computer configuration software TwinCAT on the hardware devices in the platform and realize the communication between TwinCAT and the general configuration software Kingview,which expanded the usability of the experimental platform and provided reference for the actual test of the converter field layer monitoring system. |
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